Through the use of a series of well-characterized lysozymes, their derivatives, and derived peptide fragments, we shall attempt to fully delineate the basis of immune recognition of this prototype protein. For B cells and antibody, we shall employ fine specificity analysis, idiotypy and behavior upon isoelectric focussing to delineate the specificity and basis of heterogeneity of antibody populations. For T cells, limiting dilution proliferation assays and T-rosetting will be employed to determine the size and specificity of binding sites. The contributions of antigen-bridging and idiotypic complementarity to T-T and T-B cell interactions will be studied. Through the use of lysozyme and lysozyme peptides labelled with high specific activity of radioisotope, processing at the macrophage level will be analyzed.